To assess the risk and plan interventions, we calculated the vaccination coverage for all three affected anthroposophic schools. We obtained information on vaccination through a questionnaire distributed to all pupils and through ��Vaccinnet��. ��Vaccinnet�� is a web-based vaccine ordering system as well as a computerized Ponatinib dna immunization registry for Flanders. Up to 92.5% of recent vaccinations are registered in ��Vaccinnet�� [16,17]. We used school lists to manually extract vaccination data. We calculated the vaccination coverage based on ��Vaccinnet�� and based on the questionnaire. Results Course of the outbreak At the beginning of March 2011, five cases of measles were reported to the Infectious Disease Control Unit of the Public Health Surveillance of East-Flanders.

Two cases were brothers, but there was no obvious link between the other cases. All were unvaccinated. Further investigation revealed that they had all been present at the same time on February 22nd in the waiting room of a general practitioner (GP) with an anthroposophic approach. The youngest of the five cases, a 10-month old boy (index patient) consulted the GP with signs of measles. This infant attended a day care center in Ghent. Three of the four other cases, aged 4, 9 and 12 years, went to three different anthroposophic schools. New cases (N=16) were reported two weeks later. All these new cases were linked to the ��waiting-room��-cases. All but one of these new cases went to school at one of the earlier mentioned anthroposophic schools. The only case not linked through the schools was the sibling of a ��waiting-room��-case (Figure 1).

In one anthroposophic school the outbreak was limited to one case. In the day care center a new case was reported shortly thereafter. Figure 1 Overview of the measles outbreak, Ghent, Belgium 2011. Dots represent cases (N=65). Cases that are siblings are connected by a line. Timeline is only indicative. A new generation of 18 measles cases occurred at the end of March. Eleven of these new cases were family members of known cases. One of the cases without family link was a physician working at an emergency department. She was probably infected during the clinical examination of one of the day care center-cases. In two laboratory-confirmed cases no obvious link with the current cluster could be found.

These patients were either part of a different outbreak (one of them, a 24-year old woman, was probably infected during a meeting in Paris) or linked to the outbreak in a way unknown to us. At the beginning of April, 10 new cases were reported. Eight of these cases were school contacts. Two could not be linked. From mid-April Carfilzomib on, only a three new cases were reported. These cases were laboratory confirmed but without a clear link to the outbreak. This outbreak consisted of a total of 65 cases (Figure 2). Figure 2 Epidemic curve, measles outbreak Ghent, Belgium 2011.